1. Field of the Invention
The present invention relates to a method of manufacturing homopolymers and/or copolymers, in an aqueous solution of ethylenically monounsaturated monomers, e.g. acrylic and/or vinylic monomers, such that, for each monomer, one can achieve a residual monomer concentration less than or equal to 300 ppm (based on the weight of the raw product), wherewith the concentration of the products is at least 38%; and wherewith these results can be achieved regardless of the monomer(s) used, and at the end of the polymerization, without the need for any intervening treatment.
The invention also relates to the homopolymers and/or copolymers manufactured by the described method; and the use of said homopolymers and/or copolymers, as:
milling agents and/or dispersants in aqueous suspensions of mineral materials; or PA1 sequestering agents and/or precipitation inhibitors and/or inhibitors of mineral incrustation (particularly with respect to heat transfer surfaces in industrial or household systems); or PA1 fluidifying agents for aqueous suspensions based on non-saline or saline water, which suspensions are used as drilling fluids (muds) and the like in the areas of civil engineering, construction, public works, minerals prospecting, and petroleum production; or PA1 stabilizers for suspensions of zeolites; or anti-scaling agents and dispersant agents, in detergent formulations containing hypochlorite compounds, wherewith the subject polymers do not destabilize the "chlorometric index" of said hypochlorite compounds; or PA1 "builders" in detergent compositions; or PA1 water retention agents in the paper industry. PA1 the use of metallic salts which promote decomposition reactions of hydrogen peroxide, e.g. the Fenton reaction, which often result(s) in ultimate products which are undesirably colored and which contain metal salts which are environmental pollutants; PA1 the use of persulfates which undergo decomposition because of the application of heat or because of redox reactions, resulting in ultimate products which undesirably contain sulfur; and PA1 the use of organic initiators, e.g. organic peroxides, particularly benzoyl peroxide, which result in the production of undesirable by-products such as certain nitrogen compounds. PA1 a fluidifying agent for aqueous suspensions which are used as drilling fluids (muds) and the like; or PA1 a stabilizer for suspensions of zeolites; or PA1 an anti-scaling agent and dispersant agent, for use in detergent formulations containing hypochlorite compounds, wherewith said agent does not destabilize the "chlorometric index" of said hypochlorite compounds; or PA1 a "builder" for detergent compositions and the like. PA1 in the presence of hydrogen peroxide and PA1 in the absence of any agents, which decompose hydrogen peroxide to form free radicals, such as metals or metal salts, which agents are deemed necessary by the art to satisfactorily achieve such decomposition, further, in the absence of any other generator of free radicals, and in the absence of any per salt and/or any other transfer agent. PA1 homopolymerization of a monomer such as (meth)acrylic acid or maleic acid, or PA1 copolymerization of maleic acid or a copolymerizable monomer, with acrylic acid or a copolymerizable monomer, with the addition solely of hydrogen peroxide, without the presence of agents which promote decomposition of hydrogen peroxide to form free radicals, e.g. metals or metal salts, such as salts of Cu, Fe, Co, Ni, Zn, W, Ce, Mo, Zr, or mixtures of these, which agents are deemed necessary in the art in order to satisfactorily achieve such decomposition, e.g. in the familiar Fenton reaction, and further without the presence of organic initiators, e.g. benzoyl peroxide, and further without the presence of per salts, e.g. persulfates, and further without the presence of other transfer agents e.g., thio compounds, alcohols, halides, amines, and the like. PA1 in the presence of hydrogen peroxide and PA1 in the absence of any agents which promote decomposition of hydrogen peroxide to form free radicals, and further, in the absence of any other generator of free radicals, and in the absence of any per salt and/or any other transfer agent. More particularly, in the method, all or part of the necessary quantity of the compound containing a phosphorus atom of degree of oxidation less than 5 is introduced into the reaction vessel or into the starting mixture in the reaction vessel, prior to the start of the polymerization, which introduction may occur in the presence of all or part of the monomer(s) which are to undergo polymerization, which monomer(s) if then present may be present as acids or in a partially or completely neutralized state by neutralization with a basic solution. Further the method results in the production of homopolymer(s) and/or copolymers without addition of metals or metallic salts, which metals or metallic salts initiate the decomposition of hydrogen peroxide. PA1 in the presence all or part of the monomer(s) to be polymerized, which monomer(s) if then present may be present as the acids or in a partially or completely neutralized state provided by neutralization with a basic solution, and PA1 generally in the presence of sufficient added water to obtain a homogeneous solution. PA1 all or part of the total amount of the monomer to be polymerized, PA1 all or part of the total amount of the compound containing a phosphorus atom which is sodium hypophosphite as hypophosphorous acid, in an amount determined by the desired molecular weight, and PA1 a quantity of water as needed to prepare a homogeneous solution. PA1 alkali cations, particularly those of sodium and potassium, and also ammonium ion; PA1 the primary, secondary, or tertiary amines, aliphatic and/or cyclic, e.g. mono-, di-, and triethanolamine, mono- and diethylamine, cyclohexylamine, and methylcyclohexylamine; PA1 the divalent alkaline earth cations, particularly those of magnesium and calcium, and the divalent zinc cation; PA1 the trivalent cations, particularly aluminum; certain cations of higher valence; and PA1 cations of primary and secondary amines, aliphatic and/or cyclical, e.g. cations of monoethylamine, diethylamine, cyclohexylamine, methylcyclohexylamine(s); and combinations thereof. PA1 the efflux time of a given volume of said solution containing the copolymer and PA1 the efflux time of the same volume of doubly de-ionized water, not containing the copolymer. PA1 the efflux time of a given volume of a solution of 2.5 g of the corresponding sodium polyacrylate (dry) in 50 mL of a 60 g/L aqueous solution of sodium chloride to PA1 the efflux time of an equal volume of aqueous sodium chloride solution without the polyacrylate. PA1 silicon oxide, aluminum oxide, zirconium oxide, or mixtures thereof; PA1 hard synthetic resins; and PA1 steels.
The invention further relates to the abovementioned aqueous suspensions of mineral materials, having characteristics of long term stability and high concentrations of the mineral materials; and the use of the suspensions in areas such as paper, paints and other coatings, detergents and other cleaning agents, ceramics, mineral drilling and production (e.g. drilling-mud compositions), and other sectors which employ such suspensions.
2. Description of the Background
Various methods have long been known for homopolymerization, in solution, of acrylic and/or vinylic monomers, e.g. (meth)acrylic acid, maleic anhydride, and acrylamide; and for copolymerization, in aqueous solution, of acrylic acid with monoethylenically unsaturated comonomers such as, e.g., maleic anhydride, itaconic acid, acrylamide, (acrylamidomethyl)propanesulfonic acid, and acrylate esters. However, none of these methods is entirely satisfactory in the light of current and/or expected environmental regulations, particularly regulations governing the residual monomer content in the polymer in a given application, or requirements as to the color and/or odor of the product.
Eur. Pats. 0,668,298 and 0,608,845 describe methods of copolymerization which, unless subsequent treatments are employed, result in residual monomer contents which exceed 1000 ppm. These methods would not meet the standards demanded in the current market.
Eur. Pat. 0,618,240 discloses a method enabling production of polymers with lower residual monomer content, as do Eur. Pats. 0,398,724, 0,510,831, and 0,663,408; however, all have fundamental practical disadvantages connected with the method, or disadvantages such as:
U.S. Pat. No. 4,301,266 discloses a method of manufacturing acrylic acid polymers, with the disadvantage that one must use a solvent of the isopropanol type and must operate at elevated pressure.
Also known to those skilled in the art is U.S. Pat. No. 4,621,127, which discloses a method of copolymerization. The method is costly and lengthy, and requires the use of chain regulators to prepare low molecular weight polymers.